This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We propose to evaluate calcuim absorption in infants using stable isotope methods. Calcium from a marketed infant formula and a formula containing prebiotics will be evaluated. These studies will be performed in infants of both genders who are selected to match the ethnic distribution of the greater Houston area. Absorption of calcium will be measured using multi-tracer stable isotope methods with urinary recovery of the administered isotopes. The findings from this study will provide information on the effect of prebiotics on calcium absorption in infants. Data will be compared with previous studies of human milk-fed infants. HYPOTHESIS Total calcium absorbed witll be significantly greater in the prebiotic containing infant formula than the marketed formula. Absorption from both groups will be equal or greater than that from previously studied group of human milk-fed infants. SPECIFIC AIMS The primary objective of this study is to evaluate the amount of calcium abosrbed in healthy, term infants fed either marketed cow's-milk, full lactose containing infant formula with a prebiotic blend and to determine differences in mg/100kcal of calcium absorption between two infant formulas. The secondary objective of this study are to compare the levels of plasma 25-hydroxyvitamin D, serum calcium, and 24-hour urine calcium levels between the two groups. An additional secondary objective is to compare the absorption of calcium from both formulas with calcium absorption from human milk based on data previously collected using an essentially identical protocol.